Fix CustomEventEmitter error handling

Override .emit() to first check whether the error argument is an array. In case
it is an array, reduce it to the very first error and pass it to the original
EventEmitter.emit()

lib/emitters/custom-event-emitter.js

@@ -28,6 +28,25 @@ module.exports = (function() {
     return this
   }
 
+  CustomEventEmitter.prototype.emit = function(type) {
+    this._events = this._events || {};
+
+    // Override default 'error' event logic
+    if (type === 'error' && !this._events.error) {
+      // No error listener
+      var er = arguments[1];
+
+      // If error argument is an array, make sure we
+      // pass only the first error to the original
+      // .emit() function of EventEmitter
+      if (er instanceof Array) {
+        arguments[1] = Utils._.flatten(er)[0]
+      }
+    }
+
+    EventEmitter.prototype.emit.apply(this, arguments);
+  };
+
   /**
     Shortcut methods (success, ok) for listening for success events.
 

test/emitters/custom-event-emitter.test.js

@@ -7,7 +7,7 @@ var chai      = require('chai')
 
 chai.Assertion.includeStack = true
 
-describe(Support.getTestDialectTeaser("CustomEventEmitter"), function () {
+describe.only(Support.getTestDialectTeaser("CustomEventEmitter"), function () {
   describe("proxy", function () {
     it("should correctly work with success listeners", function(done) {
       var emitter = new CustomEventEmitter()
@@ -60,4 +60,46 @@ describe(Support.getTestDialectTeaser("CustomEventEmitter"), function () {
       proxy.emit('success')
     })
   })
+
+  describe("when emitting an error event with an array of errors", function() {
+    describe("if no error handler is given", function() {
+      it("should throw the first error", function(done) {
+        var emitter = new CustomEventEmitter()
+
+        expect(function () {
+          emitter.emit("error", [
+            [
+              new Error("First error"),
+              new Error("Second error")
+            ], [
+              new Error("Third error")
+            ]
+          ])
+        }).to.throw("First error")
+
+        done()
+      })
+    })
+
+    describe("if an error handler is given", function() {
+      it("should return the whole array", function(done) {
+        var emitter = new CustomEventEmitter()
+        var errors = [
+          [
+            new Error("First error"),
+            new Error("Second error")
+          ], [
+            new Error("Third error")
+          ]
+        ]
+
+        emitter.error(function (err) {
+          expect(err).to.equal(errors)
+
+          done()
+        })
+        emitter.emit("error", errors)
+      })
+    })
+  })
 })